Controllable CSI-RS density

ABSTRACT

Methods and apparatus for configuring, in a network node of a wireless communication network, a reference signal resource. An example method comprises obtaining a combination of one or more components to be used for a reference signal resource, the one or more components being contained in one or more physical resource blocks of a slot; and indicating, to the one or more wireless devices, the combination of the one or more components in the one or more physical resource blocks that are to be used for the reference signal resource.

This application is a continuation of International Application No.PCT/IB2017/057741, filed Dec. 7, 2017, which claims the benefit of U.S.Provisional Application No. 62/560,019, filed Sep. 18, 2017, and U.S.Provisional Application No. 62/431,743, filed Dec. 8, 2016, thedisclosure of which is fully incorporated herein by reference.

TECHNICAL FIELD

The disclosed subject matter relates generally to telecommunications andmore particularly to control of Channel State Information ReferenceSignal (CSI-RS) density in channels of a next generation mobile wirelesscommunication system.

BACKGROUND

The next generation mobile wireless communication system (5G or NR),will support a diverse set of use cases and a diverse set of deploymentscenarios. The latter includes deployment at both low frequencies (100 sof MHz), similar to LTE today, and very high frequencies (mm waves inthe tens of GHz). At high frequencies, propagation characteristics makeachieving good coverage challenging. One solution to the coverage issueis to employ high-gain beamforming, typically in an analog manner, inorder to achieve satisfactory link budget. Beamforming will also be usedat lower frequencies (typically digital beamforming), and is expected tobe similar in nature to the already standardized 3GPP LTE system (4G).

For background purposes, some of the key aspects of LTE are described inthis section. Of particular relevance is the sub-section describingchannel state information reference signals (CSI-RS). A similar signalwill be designed also for NR, and is the subject of the presentapplication.

Note that terminology used here such as eNodeB and UE should beconsidering non-limiting and does in particular not imply a certainhierarchical relation between the two; in general, “eNodeB” could beconsidered as device 1 and “UE” device 2, and these two devicescommunicate with each other over some radio channel. Herein, we alsofocus on wireless transmissions in the downlink, but the invention isequally applicable in the uplink.

LTE and NR use OFDM in the downlink and DFT-spread OFDM or OFDM in theuplink. The basic LTE or NR downlink physical resource can thus be seenas a time-frequency grid as illustrated in FIG. 6, where each resourceelement corresponds to one OFDM subcarrier during one OFDM symbolinterval.

Moreover, as shown in FIG. 7, in the time domain, LTE downlinktransmissions are organized into radio frames of 10 milliseconds, eachradio frame consisting of ten equally-sized subframes of lengthT_(subframe)=1 millisecond.

Furthermore, the resource allocation in LTE is typically described interms of resource blocks, where a resource block corresponds to one slot(0.5 millisecond) in the time domain and 12 contiguous subcarriers inthe frequency domain. Resource blocks are numbered in the frequencydomain, starting with 0 from one end of the system bandwidth. For NR, aresource block is also 12 subcarriers in frequency, but the number ofOFDM symbols in the NR resource block has not yet been determined. Itwill be appreciated that the term “resource block,” as used herein, willthus refer to a block of resources spanning a certain number ofsubcarriers and a certain number of OFDM symbols—the term as used hereinmay, in some instances, refer to a different sized block of resourcesfrom what is ultimately labeled a “resource block” in the standards forNR or in the standards for some other system.

Downlink transmissions are dynamically scheduled, i.e., in each subframethe base station transmits control information about to which terminalsdata is transmitted and upon which resource blocks the data istransmitted, in the current downlink subframe. This control signaling istypically transmitted in the first 1, 2, 3 or 4 OFDM symbols in eachsubframe in LTE, and in 1 or 2 OFDM symbols in NR. A downlink systemwith 3 OFDM symbols as control is illustrated in the downlink subframeillustrated in FIG. 8.

Codebook-Based Precoding

Multi-antenna techniques can significantly increase the data rates andreliability of a wireless communication system. The performance isparticularly improved if both the transmitter and the receiver areequipped with multiple antennas, which results in a multiple-inputmultiple-output (MIMO) communication channel. Such systems and/orrelated techniques are commonly referred to as MIMO.

NR is currently evolving with MIMO support. A core component in NR isthe support of MIMO antenna deployments and MIMO related techniquesincluding beamforming at higher carrier frequencies. Currently, LTE andNR support an 8-layer spatial multiplexing mode for up to 32 Tx antennaswith channel-dependent precoding. The spatial multiplexing mode is aimedfor high data rates in favorable channel conditions. An illustration ofthe spatial multiplexing operation is provided in FIG. 9.

As seen, the information carrying symbol vector s is multiplied by anN_(T)×r precoder matrix W, which serves to distribute the transmitenergy in a subspace of the N_(T)—(corresponding to N_(T) antenna ports)dimensional vector space. The precoder matrix is typically selected froma codebook of possible precoder matrices, and typically indicated bymeans of a precoder matrix indicator (PMI), which specifies a uniqueprecoder matrix in the codebook for a given number of symbol streams.The r symbols in s each correspond to a layer and r is referred to asthe transmission rank. In this way, spatial multiplexing is achieved,since multiple symbols can be transmitted simultaneously over the sametime/frequency resource element (TFRE). The number of symbols r istypically adapted to suit the current channel properties.

LTE and NR use OFDM in the downlink and hence the received N_(R)×1vector y_(n) for a certain TFRE on subcarrier n (or alternatively dataTFRE number n) is thus modeled byy _(n) =H _(n) Ws _(n) +e _(n)where e_(n) is a noise/interference vector obtained as realizations of arandom process. The precoder, implemented by precoder matrix W, can be awideband precoder that is constant over frequency or that is frequencyselective.

The precoder matrix is often chosen to match the characteristics of theN_(R)×N_(T) MIMO channel matrix H_(n), resulting in so-calledchannel-dependent precoding. This is also commonly referred to asclosed-loop precoding and essentially strives for focusing the transmitenergy into a subspace which is strong in the sense of conveying much ofthe transmitted energy to the UE. In addition, the precoder matrix mayalso be selected to strive for orthogonalizing the channel, meaning thatafter proper linear equalization at the UE, the inter-layer interferenceis reduced.

The transmission rank, and thus the number of spatially multiplexedlayers, is reflected in the number of columns of the precoder. Forefficient performance, it is important that a transmission rank thatmatches the channel properties is selected.

Channel State Information Reference Symbols (CSI-RS)

In LTE and NR, a reference symbol sequence was introduced for thepurpose of estimating channel-state information, the CSI-RS. The CSI-RSprovides several advantages over basing the CSI feedback on the commonreference symbols (CRS) which were used, for that purpose, in previousreleases. Firstly, the CSI-RS is not used for demodulation of the datasignal, and thus does not require the same density (i.e., the overheadof the CSI-RS is substantially less). Secondly, CSI-RS provides a muchmore flexible means to configure CSI feedback measurements (e.g., whichCSI-RS resource to measure on can be configured in a UE specificmanner).

By measuring on a CSI-RS, a UE can estimate the effective channel theCSI-RS is traversing, including the radio propagation channel andantenna gains. In more mathematical rigor, this implies that if a knownCSI-RS signal x is transmitted, a UE can estimate the coupling betweenthe transmitted signal and the received signal (i.e., the effectivechannel). Hence if no virtualization is performed in the transmission,the received signal y can be expressed asy=Hx+eand the UE can estimate the effective channel H.

Up to 32 CSI-RS ports can be configured for a LTE or NR UE, that is, theUE can thus estimate the channel from up to eight transmit antennas.

An antenna port is equivalent to a reference signal resource that the UEshall use to measure the channel. Hence, a base station with twoantennas could define two CSI-RS ports, where each port is a set ofresource elements in the time frequency grid within a subframe or slot.The base station transmits each of these two reference signals from eachof the two antennas so that the UE can measure the two radio channelsand report channel state information back to the base station based onthese measurements. In LTE, CSI-RS resources with 1, 2, 4, 8, 12, 16,20, 24, 28 and 32 ports are supported.

The CSI-RS utilizes an orthogonal cover code (OCC) of length two, tooverlay two antenna ports on two consecutive REs. As seen in FIG. 10,which depicts resource element grids over an RB pair with potentialpositions for LTE Rel-9/10 UE specific RS (yellow), CSI-RS (marked witha number corresponding to the CSI-RS antenna port), and CRS (blue anddark blue), many different CSI-RS patterns are available. For the caseof 2 CSI-RS antenna ports there are 20 different patterns within asubframe. The corresponding number of patterns is 10 and 5 for 4 and 8CSI-RS antenna ports, respectively. For TDD, some additional CSI-RSpatterns are available.

The CSI reference signal configurations are given by the table below,taken from LTE specifications TS 36.211 v.12.5.0. For example, the CSIRS configuration 5 for 4 antennas ports use (k′,l′)=(9,5) in slot 1 (thesecond slot of the subframe), and according to the formulas below, port15,16, use OCC over the resource elements (k,l)=(9,5), (9,6) and port17,18 use OCC over resource elements (3,5)(3,6) respectively (assumingPRB index m=0), where k is the subcarrier index and l is the OFDM symbolindex.

The orthogonal cover code (OCC) is introduced below by the factor w_(l″)

$\mspace{20mu}{k = {k^{\prime} + {12\; m} + \left\{ {{\begin{matrix}{- 0} & {{{{for}\mspace{14mu} p} \in \left\{ {15,16} \right\}},{{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}} \\{- 6} & {{{{for}\mspace{14mu} p} \in \left\{ {17,18} \right\}},{{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}} \\{- 1} & {{{{for}\mspace{14mu} p} \in \left\{ {19,20} \right\}},{{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}} \\{- 7} & {{{{for}\mspace{14mu} p} \in \left\{ {21,22} \right\}},{{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}} \\{- 0} & {{{{for}\mspace{14mu} p} \in \left\{ {15,16} \right\}},{{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}} \\{- 3} & {{{{for}\mspace{14mu} p} \in \left\{ {17,18} \right\}},{{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}} \\{- 6} & {{{{for}\mspace{14mu} p} \in \left\{ {19,20} \right\}},{{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}} \\{- 9} & {{{{for}\mspace{14mu} p} \in \left\{ {21,22} \right\}},{{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}}\end{matrix}l} = {l^{\prime} + \left\{ {{\begin{matrix}l^{''} & {{{CSI}\mspace{14mu}{reference}\mspace{14mu}{signal}\mspace{14mu}{configurations}\mspace{14mu} 0\text{-}19},{{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}} \\{2\; l^{''}} & {{{CSI}\mspace{14mu}{reference}\mspace{14mu}{signal}\mspace{14mu}{configurations}\mspace{14mu} 20\text{-}31},{{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}} \\l^{''} & {{{CSI}\mspace{14mu}{reference}\mspace{14mu}{signal}\mspace{14mu}{configurations}\mspace{14mu} 0\text{-}27},{{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}}\end{matrix}\mspace{20mu} w_{l^{''}}} = \left\{ {{{\begin{matrix}1 & {p \in \left\{ {15,17,19,21} \right\}} \\\left( {- 1} \right)^{l^{''}} & {p \in \left\{ {16,18,20,22} \right\}}\end{matrix}\mspace{20mu} l^{''}} = 0},{{1\mspace{20mu} m} = 0},1,\ldots\mspace{14mu},{{N_{RB}^{DL} - {1\mspace{20mu} m^{\prime}}} = {m + \left\lfloor \frac{N_{RB}^{\max,{DL}} - N_{RB}^{DL}}{2} \right\rfloor}}} \right.} \right.}} \right.}}$

TABLE 6.10.5.2-1 Mapping from CSI reference signal configuration to (k′,l′) for normal cyclic prefix CSI reference Number of CSI referencesignals configured signal 1 or 2 4 8 configuration (k′, l′) n_(s) mod 2(k′, l′) n_(s) mod 2 (k′, l′) n_(s) mod 2 Frame 0 (9, 5) 0 (9, 5) 0 (9,5) 0 structure 1 (11, 2)  1 (11, 2)  1 (11, 2)  1 type 1 2 (9, 2) 1 (9,2) 1 (9, 2) 1 and 2 3 (7, 2) 1 (7, 2) 1 (7, 2) 1 4 (9, 5) 1 (9, 5) 1 (9,5) 1 5 (8, 5) 0 (8, 5) 0 6 (10, 2)  1 (10, 2)  1 7 (8, 2) 1 (8, 2) 1 8(6, 2) 1 (6, 2) 1 9 (8, 5) 1 (8, 5) 1 10 (3, 5) 0 11 (2, 5) 0 12 (5, 2)1 13 (4, 2) 1 14 (3, 2) 1 15 (2, 2) 1 16 (1, 2) 1 17 (0, 2) 1 18 (3, 5)1 19 (2, 5) 1 Frame 20 (11, 1)  1 (11, 1)  1 (11, 1)  1 structure 21(9, 1) 1 (9, 1) 1 (9, 1) 1 type 2 22 (7, 1) 1 (7, 1) 1 (7, 1) 1 only 23(10, 1)  1 (10, 1)  1 24 (8, 1) 1 (8, 1) 1 25 (6, 1) 1 (6, 1) 1 26(5, 1) 1 27 (4, 1) 1 28 (3, 1) 1 29 (2, 1) 1 30 (1, 1) 1 31 (0, 1) 12D Antenna Arrays

In LTE, support for two-dimensional antenna arrays was introduced whereeach antenna element has an independent phase and amplitude control,thereby enabling beamforming in both in the vertical and the horizontaldimensions. Such antenna arrays may be (partly) described by the numberof antenna columns corresponding to the horizontal dimension N_(h), thenumber of antenna rows corresponding to the vertical dimension N_(v),and the number of dimensions corresponding to different polarizationsN_(p). The total number of antennas is thus N=N_(h)N_(v)N_(p). Anexample of an antenna where N_(h)=8 and N_(v)=4 is illustrated in FIG.11, which illustrates on the left side thereof a two-dimensional antennaarray of cross-polarized antenna elements (N_(p)=2), with N_(h)=4horizontal antenna elements and N_(v)=8 vertical antenna elements, andon the right side of FIG. 11 the actual port layout with 2 verticalports and 4 horizontal ports is illustrated. This could for instance beobtained by virtualizing each port by 4 vertical antenna elements.Hence, assuming cross-polarized ports are present, the UE will measure16 antenna ports in this example.

However, from a standardization perspective, the actual number ofelements antenna array is not visible to the UE, but rather the antennaports, where each ports corresponds to a CSI reference signal. The UEcan thus measure the channel from each of these ports. Therefore, weintroduce a 2D port layout, described by the number of antenna ports inthe horizontal dimension M_(h), the number of antenna rows correspondingto the vertical dimension M_(v) and the number of dimensionscorresponding to different polarizations M_(p). The total number ofantenna ports is thus M=M_(h)M_(v)M_(p). The mapping of these ports onto the N antenna elements is an eNB implementation issue and thus notvisible by the UE. The UE does not even know the value of N; it onlyknows the value of the number of ports M.

Precoding may be interpreted as multiplying the signal with differentbeamforming weights for each antenna port prior to transmission. Atypical approach is to tailor the precoder to the antenna form factor,i.e. taking into account M_(h), M_(v) and M_(p) when designing theprecoder codebook.

A common approach when designing precoder codebooks tailored for 2Dantenna arrays is to combine precoders tailored for a horizontal arrayand a vertical array of antenna ports respectively by means of aKronecker product. This means that (at least part of) the precoder canbe described as a function ofW _(H) ⊗W _(V)

where W_(H) is a horizontal precoder taken from a (sub)-codebook X_(H)containing N_(H) codewords and similarly W_(V) is a vertical precodertaken from a (sub)-codebook X_(V) containing N_(V) codewords. The jointcodebook, denoted by X_(H)⊗X_(V), thus contains N_(H)·N_(V) codewords.The codewords of X_(H) are indexed with k=0, . . . , N_(H)−1, thecodewords of X_(V) are indexed with l=0, . . . , N_(V)−1 and thecodewords of the joint codebook X_(H)⊗X_(V) are indexed with m=N_(V)·k+lmeaning that m=0, . . . , N_(H)·N_(V)−1.

For LTE Rel-12 UE and earlier, only a codebook feedback for a 1D portlayout is supported, with 2,4 or 8 antenna ports. Hence, the codebook isdesigned assuming these ports are arranged on a straight line.

Periodic CSI Reporting on a Subset of 2D Antenna Ports

A method has been proposed to use measurements on fewer CSI-RS ports forperiodic CSI reports than measurements for the aperiodic CSI reports.

In one scenario, the periodic CSI report framework is identical tolegacy terminal periodic CSI report framework. Hence, periodic CSIreports with 2, 4 or 8 CSI-RS ports are used for the P-CSI reporting andadditional ports are used for the A-CSI reporting. From UE and eNBperspective, the operations related to periodic CSI reporting isidentical to legacy operation.

The full, large 2D port layout CSI measurements of up to 64 ports oreven more is only present in the aperiodic reports. Since A-CSI iscarried over PUSCH, the payload can be much larger than the small 11-bitlimit of the P-CSI using PUCCH format 2.

CSI-RS resource allocation for a 2D antenna array

It has been agreed that for 12 or 16 ports, a CSI-RS resource for classA CSI reporting is composed as an aggregation of K CSI-RS configurationseach with N ports. In case of CDM-2, the K CSI-RS resourceconfigurations indicate CSI-RS RE locations according to legacy resourceconfigurations in TS36.211. For 16 ports:(N,K)=(8,2),(2,8)

For 12 port construction:(N,K)=(4,3),(2,6)

The ports of the aggregated resource correspond to the ports ofcomponent resources according to the following:

The aggregated port numbers are 15, 16, . . . 30 (for 16 CSI-RS ports)

The aggregated port numbers are 15, 16, . . . 26 (for 12 CSI-RS ports)

CSI-RS Antenna Port Numbering

For a given P antenna ports, the Rel-10,12 and 13 precoding codebooksare designed so that the P/2 first antenna ports (e.g. 15-22) should mapto a set of co-polarized antennas and the P/2 last antenna ports (e.g.16-30) are mapped to another set of co-polarized antennas, with anorthogonal polarization to the first set. This is thus targetingcross-polarized antenna arrays. FIG. 12 illustrates antenna portnumbering for a case of P=8 ports.

Hence, the codebook principles for the rank 1 case are that a DFT “beam”vector is chosen for each set of P/2 ports and a phase shift with QPSKalphabet is used to co-phase the two sets of antenna ports. A rank 1codebook is thus constructed as

$\quad\begin{pmatrix}a \\{ae}^{i\;\omega}\end{pmatrix}$

where a is a length P/2 vector that forms a beam for the first andsecond polarizations respectively and ω is a co-phasing scalar thatco-phases the two orthogonal polarizations.

Using CSI-RS Signals in NR

In NR, the CSI-RS signal needs to be designed and used for at leastsimilar purposes as in LTE. However, the NR CSI-RS is expected tofulfill additional purposes such as beam management. Beam management isa process whereby eNB and UE beams are tracked which includes finding,maintaining, and switching between suitable beams as UEs move bothwithin and between the coverage areas of multi-beam transmit-receivepoints (TRPs). This is accomplished by UEs performing measurements onthe CSI-RS reference signals and feeding these measurements back to thenetwork for the purposes of beam management decisions.

It is thus a problem how to design a CSI-RS that can be used for “LTEtype” of functionality as well as for beam management functionality withboth digital and analog beamforming.

An additional point of difference between NR and LTE is that NR willsupport flexible numerology, i.e., scalable sub-carrier spacing (SCS)with a nominal value of 15 kHZ. The nominal value is scalable in powersof 2, i.e., f_(SC)=15*2^(n) kHz where n=−2, −1, 0, 1, 2, 3, 4, 5. Thisaffects the CSI-RS structure, as larger subcarrier spacings mean thatresource elements (REs) can become more spread out in the frequencydimension and this results in a larger distance in frequency betweenCSI-RS. It is thus a problem how to design CSI-RS to be able to adjustthe frequency density depending on the SCS.

One more possible point of difference is that NR may support a shortertransmission duration than LTE. The NR transmission duration is a slotwhere a slot can be either 7 or 14 OFDM symbols long. In contrast, thetransmission duration in LTE is fixed at one subframe which equals 14symbols.

Additionally, because there is no common reference signals (CRS) in NR,the placement of CSI-RS in NR is not restricted to avoid collisions withNR. Thus, greater flexibility may be used in the design of CSI-RS forNR.

SUMMARY

Several of the techniques and apparatus described herein address theabove issues and provide greater flexibility in the design and use ofCSI-RS for NR.

Embodiments of the presently disclosed invention include a method thatincludes a step in which a combination of one or more units orcomponents to be used for a reference signal resource is obtained. Thecombination may be obtained based on one or more criteria and/orpredetermined rules including, for example, a desired densitycharacteristic of the reference signal resource, a number of portsconfigured for one or more wireless devices by which the referencesignal resource will be used. This obtaining may comprise, for example,aggregating the one or more components across two or more physicalresource blocks, to form the reference signal resource. This aggregatingmay be done such that there is one, or several, REs per port, per PRBamong the PRBs used to carry the reference signal. This example methodfurther comprises a step in which the combination of the one or morecomponents in the one or more physical resource blocks that are to beused for the reference signal resource are indicated to one or morewireless devices.

In some embodiments of the methods summarized above, each physicalresource block spans a plurality of subcarriers, and indicating thecombination of the one or more components includes indicating one ormore subcarrier indexes. In some embodiments, the one or more subcarrierindexes are indicated to the one or more wireless devices using one ormore bitmaps. In some of these embodiments, each bit in the bitmapuniquely corresponds to a subcarrier index, such that a set bit in thebitmap indicates that a component located at a subcarrier indexcorresponding to the set bit is part of the combination of one or morecomponents used for the reference signal resource. In some embodiments,the number of bits in each of the one or more bitmaps depends on anumber of subcarriers in a component. In some embodiments, the number ofbits in each of the one or more bitmaps may be half the number ofsubcarriers in the PRB, for example.

In some embodiments, each of the components corresponds to two or moresubcarriers, the two or more subcarriers of each component beingadjacent in frequency. In some of these embodiments, each component mayalso correspond to two or more adjacent symbols.

The reference signal resource in the above method may be a CSI-RSresource, in some embodiments. This CSI-RS resource may be used by theone or more wireless devices to perform CSI measurements, for example.In some embodiments, the reference signal resource is used to perform atleast one of link adaptation for the one or more wireless devices andbeam management for the one or more wireless devices. This beammanagement may include beam selection, such as selection of a transmitbeam transmitted by a network node and/or a receive beam received by awireless device.

Other embodiments include methods of operating a wireless device. Anexample method comprises a step in which an indication is received, froma network node, of a combination of one or more components contained inone or more physical resource blocks of a slot. This example methodfurther comprises a step in which the indicated combination of one ormore components is used for a reference signal resource.

In some embodiments, the indicated combination consists of one RE perport, per physical resource block of the one or more physical resourceblocks of the slot. In some embodiments, each physical resource blockspans a plurality of subcarriers, and the indication of the combinationof the one or more components includes an indication of one or moresubcarrier indexes. In some of these latter embodiments, the indicationof the one or more subcarrier indexes may include one or more bitmaps.The number of bits in each of the one or more bitmaps may depend on anumber of subcarriers in a component. In some embodiments, each bit inthe bitmap uniquely corresponds to a subcarrier index, such that a setbit in the bitmap indicates that a component located at a subcarrierindex corresponding to the set bit is part of the combination of one ormore components used for the reference signal resource. In some of theseembodiments, the number of bits in each of the one or more bitmaps ishalf a number of subcarriers in the physical resource block.

In some embodiments, each of the components corresponds to two or moresubcarriers, the two or more subcarriers of each component beingadjacent in frequency. In some of these embodiments, each component mayalso correspond to two or more adjacent symbols.

The reference signal resource in the above methods may be a CSI-RSresource, in some embodiments. This CSI-RS resource may be used by theone or more wireless devices to perform CSI measurements, for example.In some embodiments, the reference signal resource is used to perform atleast one of link adaptation for the one or more wireless devices andbeam management for the one or more wireless devices. This beammanagement may include beam selection, such as selection of a transmitbeam transmitted by a network node and/or a receive beam received by awireless device.

Other embodiments of the present invention include apparatusescorresponding to the above-summarized methods and configured to carryout one or more of these methods, or variants thereof. Thus, embodimentsinclude a network node for use in a wireless communication network, thenetwork node being adapted to obtain a combination of one or morecomponents to be used for a reference signal resource, the one or morecomponents being contained in one or more physical resource blocks of aslot, and to indicate, to the one or more wireless devices, thecombination of the one or more components in the one or more physicalresource blocks that are to be used for the reference signal resource.Likewise, other embodiments include a wireless device adapted to receivean indication, from a network node, of a combination of one or morecomponents contained in one or more physical resource blocks of a slot,and to use the indicated combination of one or more components for areference signal resource. The variations of these techniques assummarized above and as described in further detail below are equallyapplicable to the method and apparatus embodiments disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate selected embodiments of the disclosed subjectmatter. In the drawings, like reference labels denote like features.

FIG. 1 is a diagram illustrating an LTE network.

FIG. 2 is a diagram illustrating a wireless communication device.

FIG. 3 is a diagram illustrating a radio access node.

FIG. 4 is a flowchart illustrating a method of operating a network node.

FIG. 5 is a diagram illustrating a network node.

FIG. 6 is a schematic diagram of an example Orthogonal FrequencyDivision Multiplexing (OFDM) downlink physical resource.

FIG. 7 is a schematic diagram of an example OFDM time-domain structure.

FIG. 8 is a schematic diagram of an example OFDM downlink subframe.

FIG. 9 is a functional block diagram of a spatial multiplexingoperation.

FIG. 10 is a graphical illustration of example resource element gridsover an RB pair.

FIG. 11 is a graphical illustration of an example antenna array and itscorresponding port layout.

FIG. 12 is a graphical illustration of an example numbering scheme forantenna ports.

FIG. 13 is an example signaling diagram between a radio access node of awireless communications network and a wireless communication device.

FIG. 14 is another example signaling diagram between a radio access nodeof a wireless communications network and a wireless communicationdevice.

FIG. 15 is a graphical illustration of an OFDM symbol having six CSI-RSunits in one PRB.

FIG. 16 is a graphical illustration of two different NR slot sizes andthe example location of CSI-RS units therein.

FIG. 17 is a graphical illustration of various resource allocationconfigurations in which CSI-RS units may be aggregated.

FIG. 18 is a graphical illustration of various example port numbermappings that correspond to the resource allocation configurations ofFIG. 17.

FIG. 19 is a graphical illustration of two possible comb patterns orstructures resulting from a subsampling of an aggregated CSI-RSresource.

FIG. 20 is a graphical illustration of another possible comb pattern orstructure resulting from a subsampling of an aggregated CSI-RS resource.

FIG. 21 is a graphical illustration of two different NR slot sizes andthe example location of CSI-RS units therein when two bitmaps are usedto indicate CSI-RS combinations.

FIG. 22 is a flowchart illustrating a method of operating a networknode.

FIG. 23 is a graphical illustration of a virtual network node apparatus.

FIG. 24 is a flowchart illustrating a method of operating a wirelessdevice.

FIG. 25 is a graphical illustration of a virtual wireless deviceapparatus.

FIG. 26 is a graphical illustration of an example virtualizationenvironment in which embodiments of the invention may operate.

FIG. 27 is a graphical illustration of a telecommunication networkconnected via an intermediate network to a host computer in accordancewith some embodiments.

FIG. 28 is a graphical illustration of a host computer communicating viaa base station with a user equipment over a partially wirelessconnection in accordance with some embodiments.

FIG. 29 is a flowchart illustrating a method implemented in acommunication system including a host computer, a base station and auser equipment in accordance with some embodiments.

FIG. 30 is a flowchart illustrating another method implemented in acommunication system including a host computer, a base station and auser equipment in accordance with some embodiments

DETAILED DESCRIPTION

The following description presents various embodiments of the disclosedsubject matter. These embodiments are presented as teaching examples andare not to be construed as limiting the scope of the disclosed subjectmatter. For example, certain details of the described embodiments may bemodified, omitted, or expanded upon without departing from the scope ofthe described subject matter.

Radio Node: As used herein, a “radio node” is either a radio access nodeor a wireless device.

Controlling Node: As used herein, a “controlling node” either a radioaccess node or a wireless device used to manage, control or configureanother node.

Radio Access Node: As used herein, a “radio access node” is any node ina radio access network of a cellular communications network thatoperates to wirelessly transmit and/or receive signals. Some examples ofa radio access node include, but are not limited to, a base station(e.g., an enhanced or evolved Node B (eNB) in a Third GenerationPartnership Project (3GPP) Long Term Evolution (LTE) network), ahigh-power or macro base station, a low-power base station (e.g., amicro base station, a pico base station, a home eNB, or the like), and arelay node.

Core Network Node: As used herein, a “core network node” is any type ofnode in a Core Network (CN). Some examples of a core network nodeinclude, e.g., a Mobility Management Entity (MME), an Evolved-ServingMobile Location Center (E-SMLC), a Packet Data Network (PDN) Gateway(P-GW), a Service Capability Exposure Function (SCEF), or the like.

Wireless Device: As used herein, a “wireless device” is any type ofdevice that is capable of wirelessly transmitting and/or receivingsignals to/from another wireless device or to/from a network node in acellular communications network to obtain has access to (i.e., be servedby) the cellular communications network. Some examples of a wirelessdevice include, but are not limited to, a User Equipment (UE) in a 3GPPnetwork, a Machine Type Communication (MTC) device, an NB-IoT device, aFeMTC device, etc.

Network Node: As used herein, a “network node” is any node that iseither part of the radio access network or the CN of a cellularcommunications network/system or a test equipment node.

Signaling: As used herein, “signaling” comprises any of: high-layersignaling (e.g., via Radio Resource Control (RRC) or a like),lower-layer signaling (e.g., via a physical control channel or abroadcast channel), or a combination thereof. The signaling may beimplicit or explicit. The signaling may further be unicast, multicast orbroadcast. The signaling may also be directly to another node or via athird node.

The differences between LTE and NR drive a design for CSI-RS that isvery flexible in terms of the CSI-RS resource density both in the timeand frequency dimensions. For example, for large subcarrier spacings(e.g., 240 kHz), it is necessary to have a significantly higher densityin the frequency domain than for the nominal subcarrier spacing of 15kHz so as to maintain similarly spaced samples of the frequencyselective channel. On the other hand, for beam management purposes, itis often necessary to have a fairly spare density in frequency. Hence,what is needed for NR is a very flexible and configurable/controllabledensity to suit a wide range of use cases. This high flexibility islacking from the LTE CSI-RS design.

A CSI-RS design with a highly flexible/controllable CSI-RS antenna portdensity is desirable for NR. According to some of the presentlydisclosed techniques, the density may be controlled in one or both oftwo general ways:

The number of ports assigned to an aggregated CSI-RS resource isconfigurable by the network. Fewer ports assigned to a resourcetranslates to higher port density and vice versa.

Subsampling of the aggregated CSI-RS in the frequency domain isconfigurable by network. Increased subsampling of a resource translatesto lower port density and vice versa.

Flexible/controllable CSI-RS port density allows a single CSI-RSframework to be easily adapted to suit a wide range of use cases anddeployment scenarios necessary for NR. The foregoing two general controlfeatures may be used individually or jointly to suit the scenario ofinterest. Such flexibility improves NR system performance across allsub-carrier spacings and operating carrier frequencies, for both analogbeamforming and digital front ends.

According to some embodiments of the presently disclosed techniques, abasic CSI-RS “component” or “unit” may be defined as two adjacentresource elements (REs) contained within one OFDM symbol in a slot.Examples described herein use this definition of a CSI-RS component, butembodiments of the invention are not limited to this definition. Forexample, a CSI-RS component may be defined to include more or fewer REs,e.g., four adjacent REs contained within one OFDM symbol, or twoadjacent REs contained within two adjacent OFDM symbols. The embodimentsdescribed herein with smaller components may be suitably adapted toaccommodate such larger components without loss of the advantagesdescribed herein. The use of CSI-RS components, whatever theirparticular size, facilitates a modular approach, which then can beextended to support various needs and use cases of a NR deployment. Atechnical advantage of the basic unit being two REs adjacent infrequency, for example, but in same symbol, compared to the differentapproach used in LTE, is better flexibility in overlapping these withother reference signals, such as the new tracking reference signaldesigned for NR.

The CSI-RS units may be aggregated to form a CSI-RS resource. The CSI-RSresource is signaled from the network (gNB, eNB, TRP, . . . ) to the UEand the UE then performs CSI measurements on this CSI-RS resource andthe UE feeds back CSI measurement reports to the network. The networkthen uses this information for link adaptation and/or beam selectionand/or beam management.

FIG. 13 depicts a signaling diagram between a radio access node of awireless communications network (denoted “Network/gNB”) and a wirelesscommunication device (denoted “Terminal/UE”) in which the networkconfigures CSI-RS resources for CSI feedback and transmits CSI-RS to thewireless communication device/UE. Measurements are then performed in theUE, and a CSI report is sent as feedback to the network. Data may thenbe transmitted from the radio access node to the wireless communicationdevice, e.g., based on a precoder that is determined from the CSIreports.

FIG. 14 depicts a similar signaling diagram. However, in FIG. 14, a beammanagement setup is also depicted, in which the wireless communicationdevice selects beams. More particularly, the CSI-RS resource contains Nports which are divided into B beams, so that each beam has N/B ports.The wireless communication device selects the desired subset of N/Bports, i.e. the beam, to use for the CSI feedback.

FIG. 15 depicts an OFDM symbol in a slot having six CSI-RS units thatfit within one PRB (12 subcarriers). Each different color represents adifferent unit. A length-6 bitmap may be used to indicate from thenetwork to the UE whether each of the units or combinations(aggregations) of units are part of a CSI-RS resource or not. The bitmapvalues for each individual CSI-RS unit are shown in Table 1 below.

TABLE 1 Bitmap values for each individual CSI-RS unit CSI-RS Length-6Unit Bitmap 0 100000 1 010000 2 001000 3 000100 4 000010 5 000001

Embodiments of the presently disclosed techniques are not limited tousing a length-6 bitmap as described above. For example, if a CSI-RSunit spans more than two subcarriers and/or more than one symbol, thelength of the bitmap may be reduced (e.g., a length-3 bitmap for aCSI-RS units that span four subcarriers). Thus, a number of bits in thebitmap may depend on, e.g., be inversely proportional to, a number ofsubcarriers in the unit. Additionally, if a CSI-RS unit is allowed tohave a starting subcarrier index (or anchor location) placed on a finergrid than every second subcarrier, e.g., any subcarrier, then the lengthof the bitmap could be greater than six. In this case the number ofbitmap combinations would need to be restricted to account for the factthat units cannot overlap.

As shown in FIG. 15, where the bit indices are shown on the right-handside of the figure, each bit in the bitmap uniquely corresponds to asubcarrier index, such that a set bit in the bitmap indicates that acomponent located at a subcarrier index corresponding to the set bit ispart of the combination of one or more components used for the referencesignal resource. The location of the CSI-RS units within a slot aredescribed in specifications by the “anchor locations” listed in Table 2below. In each row of this table, the first value of the anchor locationindicates a subcarrier index and the second value ‘x’ indicates an OFDMsymbol index where x={0, 1, 2, . . . , 6} in the case of a 7-symbol slotand x={0, 1, 2, . . . , 13} for the case of a 14 symbol slot. Examplelocations for a 14-symbol slot PRB, where x=10, is shown in FIG. 16. Inthe examples discussed herein, a component that starts at a subcarrierindex is said to be located at that subcarrier index. However, otherembodiments are contemplated in which the location of a component isreferenced by the subcarrier index at which the component ends. Thus, acomponent that is located at a subcarrier index may start at thesubcarrier index or end at the subcarrier index.

TABLE 2 Anchor locations for CSI-RS units. CSI-RS Anchor Unit Location 0(11, x) 1 (9, x) 2 (7, x) 3 (5, x) 4 (3, x) 5 (1, x)

A CSI-RS resource is defined as an aggregation of one or more CSI-RSunits and further also with a port assignment which is also signaledfrom the network to the UE. Moreover, a CSI-RS resource may also includethe resource blocks for which the CSI-RS resource is valid. In somecases, the CSI-RS does not span the whole system bandwidth but only apartial bandwidth. Note that the figures shown in the presentapplication only show a single or two RBs, but these RB patterns may berepeated over the whole configured set of RBs (typically the wholesystem bandwidth, or the bandwidth for which the UE supports CSImeasurements).

In the next two subsections, the flexible aggregation part is describedfollowed by the flexible port assignment part. Together these compriseone aspect of several embodiments of the presently disclosed techniquesand apparatus. Another aspect of some embodiments (flexible resourcesubsampling) is described in the 3^(rd) sub-section.

Flexible Resource Aggregation

A CSI-RS resource in several embodiments of the present invention isdefined as the flexible aggregation of (a) resource units per OFDMsymbol, and (b) OFDM symbols plus a port assignment to the aggregatedresource. The definition of the CSI-RS may possibly also include thesupported set of multiple RBs over where this CSI-RS port extends.

For (b), the aggregated OFDM symbols may be either contiguous/adjacentor non-contiguous. For ease of discussion, it is assumed that the OFDMsymbols comprising the resource are contained within the same slot.However, in some embodiments they may span more than one slot. A usecase for non-contiguous OFDM symbols in a CSI-RS resource within a slotcan be to support frequency error estimation and tracking for the UE(which requires some time spacing between the reference signals foraccuracy).

FIG. 17 shows exemplary aggregations for the case of 1, 2, and 4contiguous OFDM symbols. The bitmap at the top of each box indicates theCSI-RS units that form the basis of the aggregation per OFDM symbol. Forexample, bitmap 110011 indicates that the aggregation is formed from 4different CSI-RS units: 1 (the top two subcarriers in each OFDM symbol),2 (the next two subcarriers), 5 (the pair of subcarriers just above thebottom two subcarriers), and 6 (the bottom two subcarriers). The OFDMsymbol location for a 1 symbol CSI-RS resource may be specified by asymbol index l₀. For a 2 contiguous symbol or a 4 contiguous symbolCSI-RS resource, the symbols may be restricted to always being adjacent,in which case the symbol locations are specified by the symbol indexesl₀ and l₀+1, for a 2 symbol CSI-RS resource, or the symbol indexes l₀,l₀+1, l₀+2, and l₀+3 for a 4 symbol CSI-RS resource. The wireless devicereceiving the bitmap may be configured by the network to recognize howmany adjacent symbols the bitmap applies to.

Although the CSI-RS units that form the basis for the CSI-RS resourcemay span 1, 2, or 4 contiguous symbol indexes, a single bitmap may beused to indicate which subcarrier indexes are part of the combination ofCSI-RS units at each symbol index, as shown in examples of FIG. 17 with2 and 4 symbol aggregations. By using a single bitmap to indicate thecombination of the one or more components located in each of multiplesymbol indexes excess signaling is reduced.

With such resource aggregations that span both time (OFDM symbols) andfrequency (subcarriers, i.e. units), in some embodiments, orthogonalcover codes (OCCs) may be applied as in LTE within and/or between CSI-RSunits. The use of OCCs is useful in order to collect more energy perport if they are applied across time. If they are applied acrossfrequency, larger CSI-RS power boosting may be applied without violatinga potential fixed threshold on the peak to average power ratio acrossresource elements.

In some embodiments, the CSI-RS units of a CSI-RS resource may belocated at two different symbol index anchor locations of a slot and theCSI-RS units at each anchor location may be indicated to the UE with adifferent bitmap, e.g., a first bitmap indicating the CSI-RS units usedat a first anchor location and a second bitmap indicating the CSI-RSunits used at a second anchor location. The use of two bitmaps allowsfor more flexibility in the definition of a CSI-RS resource. Forexample, the two bitmaps facilitate separate adjustment of the CSI-RSresource at the two different anchor locations to fit around otherpossible reference signals or physical channels, either for the sameuser or different users. Moreover, the CSI-RS units at each anchorlocation may be repeated at a symbol index adjacent to the anchorlocation. In other words, each anchor location may indicate to the UE apair of adjacent symbol indexes used for CSI-RS units to the UE. Thus,two bitmaps are communicated from the network to the UE, each bitmapcorresponding to a different pair of non-adjacent symbols. The anchorlocations of the pairwise non-adjacent symbols may be specified by thesymbol indexes l₀ and l₁ where the indexes l₁ and l₀ are separated fromeach other by 2 or more indexes to accommodate a pair of symbols at eachanchor location. Example bitmaps and port number mappings for each pairof CSI-RS symbols and example locations for the pair of CSI-RS symbols,designated by indexes l₀ and l₁, are shown in FIG. 21.

Flexible Port Assignment

In order to control the port density in an aggregated CSI-RS resource, aflexible port assignment scheme is adopted in some embodiments of thepresently disclosed techniques. With this approach, a network node canassign a variable number of ports to an aggregated resource within aCSI-RS resource.

If a small number of ports is assigned to a larger aggregated resource,then a high port density is achieved, since each port is represented ina large number of resource elements. This is useful in the case of largesub-carrier spacing. Hence, it is possible to control the port density D(defined as number of resource elements per port per resource block)depending on the use case with this configuration.

Several examples are shown in each box in FIG. 17. For example, in the3rd box from the left on the bottom row, the assignment of 4 ports, 8ports, and 16 ports is shown. In each of these aggregations, there are16 REs, hence the port density, D, in the three cases is 4, 2, and 1REs/port/PRB, respectively. In all cases when the number of ports isless than the number of REs, the port density is greater than 1RE/port/PRB. This is beneficial for larger subcarrier spacings so as tomaintain similarly spaced samples of the channel in the frequency domaincompared to the case if a smaller subcarrier spacing was used.

FIG. 18 shows example port number mappings for several of the resourceallocations shown in FIG. 17. In one embodiment, the port numbers aremapped across frequency first (CSI-RS units) and then across time (OFDMsymbols). As can be seen, a given port number appears D times within theresource which is consistent with the definition of port density interms of REs/port/PRB.

Flexible Resource Subsampling

In the previous two subsections entitled “Flexible Resource Aggregation”and “Flexible Port Assignment,” methods for achieving flexible andcontrollable density D of greater than or equal to 1 RE/port/PRB isdescribed. In this subsection, a second aspect of certain embodiments isdescribed whereby flexible density reduction capable of producingdensities of less than 1 RE/port/PRB is described (D<1). This is usefulfor several purposes. One is for beam management purposes, where often abeam sweep is used to discover the “direction” of the UE for use inbeamforming future control and data transmissions. For this type ofapplication, it is useful to have a relatively sparse CSI-RS density inthe frequency dimension. A reason is that often analog beamforming isused (at high carrier frequencies such as 28 GHz), and the beam is thuswideband and the corresponding RE used for an CSI-RS antenna port can bespread out over the bandwidth (low frequency sampling rate).

Another application for spare CSI-RS density is in scenarios where thechannel varies relatively slowly in the frequency dimension, hencefrequent sampling in frequency is not necessary. A sparser pattern canlead to higher data transmission peak rates since more resources areavailable for multiplexing data symbols with the CSI-RS symbols.

Flexible and controllable density reduction also for D<1 is achieved incertain embodiments of the invention by subsampling the aggregatedCSI-RS resource by a subsampling factor SF=1, 2, 3, 4, . . . where SF=1means no subsampling and SF>1 means that a CSI-RS symbol is located atmost every SF subcarriers in the frequency domain. Subsampling resultsin a frequency “comb” structure where the spacing of the comb tines isequal to SF.

FIG. 19 shows an example comb for a 16 RE resource using SF=2 (twodifferent comb offsets that are possible for SF=2 are shown). If 16ports are assigned to this aggregated resource, then the use of SF=2results in a density of D=½ which is less than 1 RE/port/PRB as desired.

When such a comb structure is used, there are SF−1 possibilities forintroducing an offset of the comb. In FIG. 19 the two possible combpatterns are shown, one with no offset and one with offset value O=1.Use of a comb offset can be beneficial in order to allocate orthogonalcombs to two different users—another motivation for density reduction.

Note that in FIG. 19, the value m is a PRB index where m spans aparticular bandwidth. This may be the whole system bandwidth or aportion thereof, for example a partial band allocated to a given user.In this example, the CSI-RS units span two different PRBs, sincesubsampling with SF=2 is used. Generally, the number of PRBs spanned bythe CSI-RS units is equal to SF.

Yet another example of resource subsampling is shown FIG. 20 wheresubsampling factor SF=4 is used on a pattern using all 6 CSI-RS units(bitmap=111111) and 2 ports are assigned. With zero samples in betweenthe “stripes” in this figure, the pattern is referred to as interleavedfrequency division multiple access (IFDMA). This type of pattern isuseful for beam sweeping operations performed in the context of beammanagement. Here, a different eNB transmit (Tx) beam can be used in eachOFDM symbol. Then within each OFDM symbol, the UE can sweep its Rx beam4 times (equal to the SF) since the IFDMA pattern creates a periodictime domain waveform with period=4 within each OFDM symbol.

Sub-sampling may alternatively be done on a per PRB basis rather than aper RE basis. For example, if a subsampling factor SF=2 is used, thenthe CSI-RS symbols are located in every second PRB and a CSI-RS densityof D=½ is achieved. Additionally, a comb offset (in number of PRBs) canbe used in a similar way as for an RE-level comb. However, the comboffset would be measured in number of PRBs (1, . . . , SF−1) rather thannumber of REs.

Using the above techniques allows for a very flexible and scalabledefinition of an CSI-RS resource for NR which can support a wide rangeof carrier frequencies (1-100 GHz), implementation choices (digital oranalog beamforming). For example, embodiments of the presently disclosedtechniques allow for definition of the CSI-RS resource according to oneor more of the following aspects:

Aggregated resource units in frequency domain (one OFDM symbol)

Described by a length-6 bitmap indicating a particular combination ofunit 1, 2, 3, 4, 5, and 6

Aggregated resource units in time domain

OFDM symbol indices over which to aggregate

Number of ports assigned to the aggregated resource

Subsample factor SF=1, 2, 3, 4, . . . and Comb Offset=0, 1, . . . , SF−1

A frequency band for which the CSI-RS resource is allocated (partialband, whole band)

OCC configuration (if used)

The described embodiments may be implemented in any appropriate type ofcommunication system supporting any suitable communication standards andusing any suitable components. As one example, certain embodiments maybe implemented in an LTE network, such as that illustrated in FIG. 1.

Referring to FIG. 1, a communication network 100 comprises a pluralityof wireless communication devices 105 (e.g., conventional UEs, machinetype communication [MTC]/machine-to-machine [M2M] UEs) and a pluralityof radio access nodes 110 (e.g., eNodeBs or other base stations).Communication network 100 is organized into cells 115, which areconnected to a core network 120 via corresponding radio access nodes110. Radio access nodes 110 are capable of communicating with wirelesscommunication devices 105 along with any additional elements suitable tosupport communication between wireless communication devices or betweena wireless communication device and another communication device (suchas a landline telephone).

Although wireless communication devices 105 may represent communicationdevices that include any suitable combination of hardware and/orsoftware, these wireless communication devices may, in certainembodiments, represent devices such as an example wireless communicationdevice illustrated in greater detail by FIG. 2. Similarly, although theillustrated radio access node may represent network nodes that includeany suitable combination of hardware and/or software, these nodes may,in particular embodiments, represent devices such as the example radioaccess node illustrated in greater detail by FIG. 3.

Referring to FIG. 2, a wireless communication device 200 comprises aprocessor 205, a memory, a transceiver 215, and an antenna 220. Incertain embodiments, some or all of the functionality described as beingprovided by UEs, MTC or M2M devices, and/or any other types of wirelesscommunication devices may be provided by the device processor executinginstructions stored on a computer-readable medium, such as the memoryshown in FIG. 2. Alternative embodiments may include additionalcomponents beyond those shown in FIG. 2 that may be responsible forproviding certain aspects of the device's functionality, including anyof the functionality described herein and in particular in FIG. 24. Itwill be appreciated that the device processor 205 may comprise one ormore microprocessors, microcontrollers, digital signal processors, andthe like, with these one or more processing elements being configured toexecute program code stored in memory 210, to control the transceiver215 and to execute all or some of the functionality described herein,and may include, in some embodiments, hard-coded digital logic thatcarries out all or some of the functionality described herein, e.g.,including the process steps shown in FIG. 24. The term “processingcircuit” is used herein to refer to any one of these combinations ofprocessing elements.

Referring to FIG. 3, a radio access node 300 comprises a node processor305, a memory 310, a network interface 315, a transceiver 320, and anantenna 325. Again, it will be appreciated that the node processor 305may comprise one or more microprocessors, microcontrollers, digitalsignal processors, and the like, with these one or more processingelements being configured to execute program code stored in memory 310,to control the transceiver 320 and the network 315 and to execute all orsome of the functionality described herein, and may include, in someembodiments, hard-coded digital logic that carries out all or some ofthe functionality described herein. This functionality includes, forexample, the operations shown in the flowcharts of FIGS. 4, 5, and 22.The term “processing circuit” is used herein to refer to any one ofthese combinations of processing elements.

Thus, in certain embodiments, some or all of the functionality describedas being provided by a base station, a node B, an enodeB, and/or anyother type of network node may be provided by node processor 305executing instructions stored on a computer-readable medium, such asmemory 310 shown in FIG. 3. Again, this functionality includes, forexample, the operations shown in the flowcharts of FIGS. 4, 5, and 22.Alternative embodiments of radio access node 300 may comprise additionalcomponents to provide additional functionality, such as thefunctionality described herein and/or related supporting functionality.

FIG. 4 is a flowchart illustrating an example method 400 of operating anetwork node (e.g., a radio access node 110). The method 400 comprises astep 405 in which a reference signal resource is aggregated in one ormore of a frequency and a time domain. The method further comprises astep 410 in which a density characteristic of the aggregated referencesignal resource that is to be transmitted to the one or more wirelessdevices (105) is adjusted. The method further comprises a step 415 inwhich a reference signal is transmitted to each of the one or morewireless devices (105), using the aggregated reference signal resourcewith the adjusted density characteristic. The method may still furthercomprise, in some embodiments, signaling an indication of the aggregatedreference signal resource with the density characteristic to the one ormore wireless devices (105).

FIG. 5 illustrates another flowchart, this flowchart showing an examplemethod 500, in a network node (110) of a wireless communication network,of selectively configuring variable density reference signal resourcesused to transmit reference signals for measurement by a wireless devicein the wireless communications network, according to one or more of thetechniques described herein.

As seen at block 510, the illustrated method comprises selecting aresource aggregation from among a plurality of resource aggregations,where each of the plurality of differing resource aggregations has adiffering number of resource units and comprises a first number i ofOFDM symbols that carry resource units within each transmission slot anda second number j of resource units per each of the first number of OFDMsymbols, per each of one or more resource blocks. Each resource blockcomprises a predetermined number of subcarriers in the frequency domainand spans a transmission slot in the time domain.

As seen at block 520, the method further comprises selecting a thirdnumber p of ports, among which the resource units within each resourceblock are allocated. With the performing of the steps shown in blocks510 and 520, as described above, a reference signal resourceconfiguration having a reference signal port density D per resourceblock is thereby configured.

As seen at block 540, the method further comprises transmitting, foreach of the p ports, a reference signal to the wireless device in atleast one transmission slot, using the resource units allocated to therespective port in the plurality of resource blocks. In someembodiments, the method may further comprise signaling an indication ofthe reference signal resource configuration to the wireless device, asshown at block 530.

In some embodiments, the resource units referred to above each consistof two adjacent OFDM resource elements. In some embodiments, the firstnumber i of OFDM symbols within each transmission slot are contiguous.

In some embodiments, transmitting the reference signal for each of the pports comprises applying an orthogonal cover code to a predeterminedsignal sequence before transmitting the reference signal. In someembodiments, the method further comprises selecting a subsampling factorSF from a plurality of subsampling factors, each subsampling factorcorresponding to a different minimum spacing of reference signal symbolsin the frequency domain, thereby defining a reduced density referencesignal configuration having a reduced reference signal port density D′per resource block, where D′=D/SF. In these embodiments, transmittingthe reference signal to the wireless device in at least one transmissionslot comprises transmitting the reference signals according to thereduced density reference signal configuration.

FIG. 22 is a flowchart illustrating another method 2200 of operating anetwork node. The method 2200 comprises a step S2205 in which acombination of one or more units or components to be used for areference signal resource is obtained. The combination may be obtainedbased on one or more criteria and/or predetermined rules including, forexample, a desired density characteristic of the reference signalresource, a number of ports configured for one or more wireless devicesby which the reference signal resource will be used. As discussed above,this obtaining may comprise aggregating the one or more componentsacross two or more physical resource blocks, to form the referencesignal resource. This aggregating may be done such that there is one, orseveral, REs per port, per PRB among the PRBs used to carry thereference signal. The method further comprises a step S2210 in which thecombination of the one or more components in the one or more physicalresource blocks that are to be used for the reference signal resourceare indicated to one or more wireless devices (105).

In some embodiments of the method illustrated generally in FIG. 22, eachphysical resource block spans a plurality of subcarriers, and indicatingthe combination of the one or more components includes indicating one ormore subcarrier indexes. In some embodiments, the one or more subcarrierindexes are indicated to the one or more wireless devices using one ormore bitmaps. In some of these embodiments, each bit in the bitmapuniquely corresponds to a subcarrier index, such that a set bit in thebitmap indicates that a component located at a subcarrier indexcorresponding to the set bit is part of the combination of one or morecomponents used for the reference signal resource. In some embodiments,the number of bits in each of the one or more bitmaps depends on anumber of subcarriers in a component. In some embodiments, the number ofbits in each of the one or more bitmaps may be half the number ofsubcarriers in the PRB, for example.

In some embodiments, each of the components corresponds to two or moresubcarriers, the two or more subcarriers of each component beingadjacent in frequency. In some of these embodiments, each component mayalso correspond to two or more adjacent symbols.

The reference signal resource in the above method may be a CSI-RSresource, in some embodiments. This CSI-RS resource may be used by theone or more wireless devices to perform CSI measurements, for example.In some embodiments, the reference signal resource is used to perform atleast one of link adaptation for the one or more wireless devices andbeam management for the one or more wireless devices. This beammanagement may include beam selection, such as selection of a transmitbeam transmitted by a network node and/or a receive beam received by awireless device.

FIG. 23 illustrates a schematic block diagram of an apparatus 2300 in awireless network (for example, the wireless network shown in FIG. 1).The apparatus may be implemented in a network node (e.g., network node110 shown in FIG. 1). Apparatus 2300 is operable to carry out theexample method described with reference to FIG. 22 and possibly anyother processes or methods disclosed herein. It is also to be understoodthat the method of FIG. 22 is not necessarily carried out solely byapparatus 2300. At least some operations of the method can be performedby one or more other entities.

Virtual Apparatus 2300 may comprise processing circuitry, which mayinclude one or more microprocessor or microcontrollers, as well as otherdigital hardware, which may include digital signal processors (DSPs),special-purpose digital logic, and the like. The processing circuitrymay be configured to execute program code stored in memory, which mayinclude one or several types of memory such as read-only memory (ROM),random-access memory, cache memory, flash memory devices, opticalstorage devices, etc. Program code stored in memory includes programinstructions for executing one or more telecommunications and/or datacommunications protocols as well as instructions for carrying out one ormore of the techniques described herein, in several embodiments. In someimplementations, the processing circuitry may be used to perform thefunctionality of obtaining unit 2305 and indicating unit 2310, and anyother suitable units of apparatus 2300 to perform correspondingfunctions according to one or more embodiments of the presentdisclosure.

As illustrated in FIG. 23, apparatus 2300 includes obtaining unit 2305and indicating unit 2310. Obtaining unit 2305 is configured to obtain acombination of one or more units or components to be used for areference signal resource and indicating unit 2310 is configured toindicate the combination of the one or more components in the one ormore physical resource blocks that are to be used for the referencesignal resource to one or more wireless devices (105).

FIG. 24 is a flowchart illustrating a method 2400 of operating awireless device. The method 2400 comprises a step S2405 in which anindication is received, from a network node, of a combination of one ormore components contained in one or more physical resource blocks of aslot. The method further comprises a step S2410 in which the indicatedcombination of one or more components is used for a reference signalresource.

In some embodiments, the indicated combination consists of one RE perport, per physical resource block of the one or more physical resourceblocks of the slot. In some embodiments, each physical resource blockspans a plurality of subcarriers, and the indication of the combinationof the one or more components includes an indication of one or moresubcarrier indexes. In some of these latter embodiments, the indicationof the one or more subcarrier indexes may include one or more bitmaps.The number of bits in each of the one or more bitmaps may depend on anumber of subcarriers in a component. In some embodiments, each bit inthe bitmap uniquely corresponds to a subcarrier index, such that a setbit in the bitmap indicates that a component located at a subcarrierindex corresponding to the set bit is part of the combination of one ormore components used for the reference signal resource. In some of theseembodiments, the number of bits in each of the one or more bitmaps ishalf a number of subcarriers in the physical resource block.

In some embodiments, each of the components corresponds to two or moresubcarriers, the two or more subcarriers of each component beingadjacent in frequency. In some of these embodiments, each component mayalso correspond to two or more adjacent symbols.

The reference signal resource in the above method may be a CSI-RSresource, in some embodiments. This CSI-RS resource may be used by theone or more wireless devices to perform CSI measurements, for example.In some embodiments, the reference signal resource is used to perform atleast one of link adaptation for the one or more wireless devices andbeam management for the one or more wireless devices. This beammanagement may include beam selection, such as selection of a transmitbeam transmitted by a network node and/or a receive beam received by thewireless device.

FIG. 25 illustrates a schematic block diagram of an apparatus 2500 in awireless network (for example, the wireless network shown in FIG. 1).The apparatus may be implemented in a wireless device (e.g., wirelessdevice 105 shown in FIGS. 1 and 2). Apparatus 2300 is operable to carryout the example methods described with reference to FIGS. 4, 5, and 24,and possibly any other processes or methods disclosed herein. It is alsoto be understood that the method of FIG. 24 is not necessarily carriedout solely by apparatus 2500. At least some operations of the method canbe performed by one or more other entities.

Virtual Apparatus 2500 may comprise processing circuitry, which mayinclude one or more microprocessor or microcontrollers, as well as otherdigital hardware, which may include digital signal processors (DSPs),special-purpose digital logic, and the like. The processing circuitrymay be configured to execute program code stored in memory, which mayinclude one or several types of memory such as read-only memory (ROM),random-access memory, cache memory, flash memory devices, opticalstorage devices, etc. Program code stored in memory includes programinstructions for executing one or more telecommunications and/or datacommunications protocols as well as instructions for carrying out one ormore of the techniques described herein, in several embodiments. In someimplementations, the processing circuitry may be used to perform thefunctionality of receiving unit 2505 and using unit 2510, and any othersuitable units of apparatus 2500 to perform corresponding functionsaccording to one or more embodiments of the present disclosure.

As illustrated in FIG. 25, apparatus 2500 includes receiving unit 2505and using unit 2510. Receiving unit 2505 is configured to receive anindication, from a network node, of a combination of one or morecomponents contained in one or more physical resource blocks of a slot.Using unit 2510 is configured to use the indicated combination of one ormore components for a reference signal resource.

The term unit may have conventional meaning in the field of electronics,electrical devices and/or electronic devices and may include, forexample, electrical and/or electronic circuitry, devices, modules,processors, memories, logic solid state and/or discrete devices,computer programs or instructions for carrying out respective tasks,procedures, computations, outputs, and/or displaying functions, and soon, as such as those that are described herein.

Operation in Virtualization Environments

FIG. 26 is a schematic block diagram illustrating a virtualizationenvironment 2600 in which functions implemented by some embodiments maybe virtualized. In the present context, virtualizing means creatingvirtual versions of apparatuses or devices which may includevirtualizing hardware platforms, storage devices and networkingresources. As used herein, virtualization can be applied to a node(e.g., a virtualized base station or a virtualized radio access node) orto a device (e.g., a UE, a wireless device or any other type ofcommunication device) or components thereof and relates to animplementation in which at least a portion of the functionality isimplemented as one or more virtual components (e.g., via one or moreapplications, components, functions, virtual machines or containersexecuting on one or more physical processing nodes in one or morenetworks).

In some embodiments, some or all of the functions described herein maybe implemented as virtual components executed by one or more virtualmachines implemented in one or more virtual environments 2600 hosted byone or more of hardware nodes 2630. Further, in embodiments in which thevirtual node is not a radio access node or does not require radioconnectivity (e.g., a core network node), then the network node may beentirely virtualized.

The functions may be implemented by one or more applications 2620 (whichmay alternatively be called software instances, virtual appliances,network functions, virtual nodes, virtual network functions, etc.)operative to implement some of the features, functions, and/or benefitsof some of the embodiments disclosed herein. Applications 2620 are runin virtualization environment 2600 which provides hardware 2630comprising processing circuitry 2660 and memory 2690. Memory 2690contains instructions 2695 executable by processing circuitry 2660whereby application 2620 is operative to provide one or more of thefeatures, benefits, and/or functions disclosed herein.

Virtualization environment 2600, comprises general-purpose orspecial-purpose network hardware devices 2630 comprising a set of one ormore processors or processing circuitry 2660, which may be commercialoff-the-shelf (COTS) processors, dedicated Application SpecificIntegrated Circuits (ASICs), or any other type of processing circuitryincluding digital or analog hardware components or special purposeprocessors. Each hardware device may comprise memory 2690-1 which may benon-persistent memory for temporarily storing instructions 2695 orsoftware executed by processing circuitry 2660. Each hardware device maycomprise one or more network interface controllers (NICs) 2670, alsoknown as network interface cards, which include physical networkinterface 2680. Each hardware device may also include non-transitory,persistent, machine-readable storage media 2690-2 having stored thereinsoftware 2695 and/or instructions executable by processing circuitry2660. Software 2695 may include any type of software including softwarefor instantiating one or more virtualization layers 2650 (also referredto as hypervisors), software to execute virtual machines 2640 as well assoftware allowing it to execute functions, features and/or benefitsdescribed in relation with some embodiments described herein.

Virtual machines 2640, comprise virtual processing, virtual memory,virtual networking or interface and virtual storage, and may be run by acorresponding virtualization layer 2650 or hypervisor. Differentembodiments of the instance of virtual appliance 2620 may be implementedon one or more of virtual machines 2640, and the implementations may bemade in different ways.

During operation, processing circuitry 2660 executes software 2695 toinstantiate the hypervisor or virtualization layer 2650, which maysometimes be referred to as a virtual machine monitor (VMM).Virtualization layer 2650 may present a virtual operating platform thatappears like networking hardware to virtual machine 2640.

As shown in FIG. 26, hardware 2630 may be a standalone network node withgeneric or specific components. Hardware 2630 may comprise antenna 26225and may implement some functions via virtualization. Alternatively,hardware 2630 may be part of a larger cluster of hardware (e.g. such asin a data center or customer premise equipment (CPE)) where manyhardware nodes work together and are managed via management andorchestration (MANO) 26100, which, among others, oversees lifecyclemanagement of applications 2620.

Virtualization of the hardware is in some contexts referred to asnetwork function virtualization (NFV). NFV may be used to consolidatemany network equipment types onto industry standard high-volume serverhardware, physical switches, and physical storage, which can be locatedin data centers, and customer premise equipment.

In the context of NFV, virtual machine 2640 may be a softwareimplementation of a physical machine that runs programs as if they wereexecuting on a physical, non-virtualized machine. Each of virtualmachines 2640, and that part of hardware 2630 that executes that virtualmachine, be it hardware dedicated to that virtual machine and/orhardware shared by that virtual machine with others of the virtualmachines 2640, forms a separate virtual network elements (VNE).

Still in the context of NFV, Virtual Network Function (VNF) isresponsible for handling specific network functions that run in one ormore virtual machines 2640 on top of hardware networking infrastructure2630 and corresponds to application 2620 in FIG. 26.

In some embodiments, one or more radio units 26200 that each include oneor more transmitters 26220 and one or more receivers 26210 may becoupled to one or more antennas 26225. Radio units 26200 may communicatedirectly with hardware nodes 2630 via one or more appropriate networkinterfaces and may be used in combination with the virtual components toprovide a virtual node with radio capabilities, such as a radio accessnode or a base station.

In some embodiments, some signaling can be effected with the use ofcontrol system 26230 which may alternatively be used for communicationbetween the hardware nodes 2630 and radio units 26200.

Operation with Remote Host Computers

With reference to FIG. 27, in accordance with an embodiment, acommunication system includes telecommunication network 2710, such as a3GPP-type cellular network, which comprises access network 2711, such asa radio access network, and core network 2714. Access network 2711comprises a plurality of base stations 2712 a, 2712 b, 2712 c, such asNBs, eNBs, gNBs or other types of wireless access points, each defininga corresponding coverage area 2713 a, 2713 b, 2713 c. Each base station2712 a, 2712 b, 2712 c is connectable to core network 2714 over a wiredor wireless connection 2715. A first UE 2791 located in coverage area2713 c is configured to wirelessly connect to, or be paged by, thecorresponding base station 2712 c. A second UE 2792 in coverage area2713 a is wirelessly connectable to the corresponding base station 2712a. While a plurality of UEs 2791, 2792 are illustrated in this example,the disclosed embodiments are equally applicable to a situation where asole UE is in the coverage area or where a sole UE is connecting to thecorresponding base station 2712.

Telecommunication network 2710 is itself connected to host computer2730, which may be embodied in the hardware and/or software of astandalone server, a cloud-implemented server, a distributed server oras processing resources in a server farm. Host computer 2730 may beunder the ownership or control of a service provider, or may be operatedby the service provider or on behalf of the service provider.Connections 2721 and 2722 between telecommunication network 2710 andhost computer 2730 may extend directly from core network 2714 to hostcomputer 2730 or may go via an optional intermediate network 2720.Intermediate network 2720 may be one of, or a combination of more thanone of, a public, private or hosted network; intermediate network 2720,if any, may be a backbone network or the Internet; in particular,intermediate network 2720 may comprise two or more sub-networks (notshown).

The communication system of FIG. 27 as a whole enables connectivitybetween the connected UEs 2791, 2792 and host computer 2730. Theconnectivity may be described as an over-the-top (OTT) connection 2750.Host computer 2730 and the connected UEs 2791, 2792 are configured tocommunicate data and/or signaling via OTT connection 2750, using accessnetwork 2711, core network 2714, any intermediate network 2720 andpossible further infrastructure (not shown) as intermediaries. OTTconnection 2750 may be transparent in the sense that the participatingcommunication devices through which OTT connection 2750 passes areunaware of routing of uplink and downlink communications. For example,base station 2712 may not or need not be informed about the past routingof an incoming downlink communication with data originating from hostcomputer 2730 to be forwarded (e.g., handed over) to a connected UE2791. Similarly, base station 2712 need not be aware of the futurerouting of an outgoing uplink communication originating from the UE 2791towards the host computer 2730.

Example implementations, in accordance with an embodiment, of the UE,base station and host computer discussed in the preceding paragraphswill now be described with reference to FIG. 28. In communication system2800, host computer 2810 comprises hardware 2815 including communicationinterface 2816 configured to set up and maintain a wired or wirelessconnection with an interface of a different communication device ofcommunication system 2800. Host computer 2810 further comprisesprocessing circuitry 2818, which may have storage and/or processingcapabilities. In particular, processing circuitry 2818 may comprise oneor more programmable processors, application-specific integratedcircuits, field programmable gate arrays or combinations of these (notshown) adapted to execute instructions. Host computer 2810 furthercomprises software 2811, which is stored in or accessible by hostcomputer 2810 and executable by processing circuitry 2818. Software 2811includes host application 2812. Host application 2812 may be operable toprovide a service to a remote user, such as UE 2830 connecting via OTTconnection 2850 terminating at UE 2830 and host computer 2810. Inproviding the service to the remote user, host application 2812 mayprovide user data which is transmitted using OTT connection 2850.

Communication system 2800 further includes base station 2820 provided ina telecommunication system and comprising hardware 2825 enabling it tocommunicate with host computer 2810 and with UE 2830. Hardware 2825 mayinclude communication interface 2826 for setting up and maintaining awired or wireless connection with an interface of a differentcommunication device of communication system 2800, as well as radiointerface 2827 for setting up and maintaining at least wirelessconnection 2870 with UE 2830 located in a coverage area (not shown inFIG. 28) served by base station 2820. Communication interface 2826 maybe configured to facilitate connection 2860 to host computer 2810.Connection 2860 may be direct or it may pass through a core network (notshown in FIG. 28) of the telecommunication system and/or through one ormore intermediate networks outside the telecommunication system. In theembodiment shown, hardware 2825 of base station 2820 further includesprocessing circuitry 2828, which may comprise one or more programmableprocessors, application-specific integrated circuits, field programmablegate arrays or combinations of these (not shown) adapted to executeinstructions. Base station 2820 further has software 2821 storedinternally or accessible via an external connection.

Communication system 2800 further includes UE 2830 already referred to.Its hardware 2835 may include radio interface 2837 configured to set upand maintain wireless connection 2870 with a base station serving acoverage area in which UE 2830 is currently located. Hardware 2835 of UE2830 further includes processing circuitry 2838, which may comprise oneor more programmable processors, application-specific integratedcircuits, field programmable gate arrays or combinations of these (notshown) adapted to execute instructions. UE 2830 further comprisessoftware 2831, which is stored in or accessible by UE 2830 andexecutable by processing circuitry 2838. Software 2831 includes clientapplication 2832. Client application 2832 may be operable to provide aservice to a human or non-human user via UE 2830, with the support ofhost computer 2810. In host computer 2810, an executing host application2812 may communicate with the executing client application 2832 via OTTconnection 2850 terminating at UE 2830 and host computer 2810. Inproviding the service to the user, client application 2832 may receiverequest data from host application 2812 and provide user data inresponse to the request data. OTT connection 2850 may transfer both therequest data and the user data. Client application 2832 may interactwith the user to generate the user data that it provides.

It is noted that host computer 2810, base station 2820 and UE 2830illustrated in FIG. 28 may be similar or identical to host computer2730, one of base stations 2712 a, 2712 b, 2712 c and one of UEs 2791,2792 of FIG. 27, respectively. This is to say, the inner workings ofthese entities may be as shown in FIG. 28 and independently, thesurrounding network topology may be that of FIG. 27.

In FIG. 28, OTT connection 2850 has been drawn abstractly to illustratethe communication between host computer 2810 and UE 2830 via basestation 2820, without explicit reference to any intermediary devices andthe precise routing of messages via these devices. Networkinfrastructure may determine the routing, which it may be configured tohide from UE 2830 or from the service provider operating host computer2810, or both. While OTT connection 2850 is active, the networkinfrastructure may further take decisions by which it dynamicallychanges the routing (e.g., on the basis of load balancing considerationor reconfiguration of the network).

Wireless connection 2870 between UE 2830 and base station 2820 is inaccordance with the teachings of the embodiments described throughoutthis disclosure. One or more of the various embodiments improve theperformance of OTT services provided to UE 2830 using OTT connection2850, in which wireless connection 2870 forms the last segment. Moreprecisely, the teachings of these embodiments may improve the data rate,among other things, and thereby provide benefits such as relaxedrestrictions on file size/resolution and better responsiveness.

A measurement procedure may be provided for the purpose of monitoringdata rate, latency and other factors on which the one or moreembodiments improve. There may further be an optional networkfunctionality for reconfiguring OTT connection 2850 between hostcomputer 2810 and UE 2830, in response to variations in the measurementresults. The measurement procedure and/or the network functionality forreconfiguring OTT connection 2850 may be implemented in software 2811and hardware 2815 of host computer 2810 or in software 2831 and hardware2835 of UE 2830, or both. In embodiments, sensors (not shown) may bedeployed in or in association with communication devices through whichOTT connection 2850 passes; the sensors may participate in themeasurement procedure by supplying values of the monitored quantitiesexemplified above, or supplying values of other physical quantities fromwhich software 2811, 2831 may compute or estimate the monitoredquantities. The reconfiguring of OTT connection 2850 may include messageformat, retransmission settings, preferred routing etc.; thereconfiguring need not affect base station 2820, and it may be unknownor imperceptible to base station 2820. Such procedures andfunctionalities may be known and practiced in the art. In certainembodiments, measurements may involve proprietary UE signalingfacilitating host computer 2810's measurements of throughput,propagation times, latency and the like. The measurements may beimplemented in that software 2811 and 2831 causes messages to betransmitted, in particular empty or ‘dummy’ messages, using OTTconnection 2850 while it monitors propagation times, errors etc.

FIG. 29 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station and a UEwhich may be those described with reference to FIGS. 27 and 28. Forsimplicity of the present disclosure, only drawing references to FIG. 29will be included in this section. In step 2910, the host computerprovides user data. In substep 2911 (which may be optional) of step2910, the host computer provides the user data by executing a hostapplication. In step 2920, the host computer initiates a transmissioncarrying the user data to the UE. In step 2930 (which may be optional),the base station transmits to the UE the user data which was carried inthe transmission that the host computer initiated, in accordance withthe teachings of the embodiments described throughout this disclosure.In step 2940 (which may also be optional), the UE executes a clientapplication associated with the host application executed by the hostcomputer.

FIG. 30 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station and a UEwhich may be those described with reference to FIGS. 27 and 28. Forsimplicity of the present disclosure, only drawing references to FIG. 30will be included in this section. In step 3010 of the method, the hostcomputer provides user data. In an optional substep (not shown) the hostcomputer provides the user data by executing a host application. In step3020, the host computer initiates a transmission carrying the user datato the UE. The transmission may pass via the base station, in accordancewith the teachings of the embodiments described throughout thisdisclosure. In step 3030 (which may be optional), the UE receives theuser data carried in the transmission

As described above, the exemplary embodiments provide both methods andcorresponding apparatuses consisting of various modules providingfunctionality for performing the steps of the methods. The modules maybe implemented as hardware (embodied in one or more chips including anintegrated circuit such as an application specific integrated circuit),or may be implemented as software or firmware for execution by aprocessor. In particular, in the case of firmware or software, theexemplary embodiments can be provided as a computer program productincluding a computer-readable storage medium embodying computer programcode (i.e., software or firmware) thereon for execution by the computerprocessor. The computer readable storage medium may be non-transitory(e.g., magnetic disks; optical disks; read only memory; flash memorydevices; phase-change memory) or transitory (e.g., electrical, optical,acoustical or other forms of propagated signals-such as carrier waves,infrared signals, digital signals, etc.). The coupling of a processorand other components is typically through one or more busses or bridges(also termed bus controllers). The storage device and signals carryingdigital traffic respectively represent one or more non-transitory ortransitory computer readable storage medium. Thus, the storage device ofa given electronic device typically stores code and/or data forexecution on the set of one or more processors of that electronic devicesuch as a controller.

Although the embodiments and its advantages have been described indetail, it should be understood that various changes, substitutions, andalterations can be made herein without departing from the spirit andscope thereof as defined by the appended claims. For example, many ofthe features and functions discussed above can be implemented insoftware, hardware, or firmware, or a combination thereof. Also, many ofthe features, functions, and steps of operating the same may bereordered, omitted, added, etc., and still fall within the broad scopeof the various embodiments.

EXAMPLE EMBODIMENTS

While not being limited thereto, some example embodiments of thepresently disclosed techniques and apparatus are provided below.

1. A method (400) of configuring, in a network node (110) of a wirelesscommunication network (100), a reference signal resource in the wirelesscommunication network (100), the method comprising:

obtaining (S2205) a combination of one or more components to be used fora reference signal resource, the one or more components being containedin one or more physical resource blocks of a slot; and

indicating (S2210), to the one or more wireless devices (105), thecombination of the one or more components in the one or more physicalresource blocks that are to be used for the reference signal resource.

2. The method of example embodiment 1, wherein the physical resourceblock spans a plurality of subcarriers, and wherein indicating thecombination of the one or more components includes indicating one ormore subcarrier indexes.

3. The method of example embodiment 2, wherein the one or moresubcarrier indexes are indicated to the one or more wireless devicesusing one or more bitmaps.

4. The method of example embodiment 3, wherein each bit in the bitmapuniquely corresponds to a subcarrier index, such that a set bit in thebitmap indicates that a component located at a subcarrier indexcorresponding to the set bit is part of the combination of one or morecomponents used for the reference signal resource.

5. The method of example embodiment 3, wherein a number of bits in eachof the one or more bitmaps depends on a number of subcarriers in acomponent.

6. The method of example embodiment 5, wherein a number of bits in eachof the one or more bitmaps is half a number of subcarriers in thephysical resource block.

7. The method of example embodiment 5, wherein a number of bits in eachof the one or more bitmaps is equal to one less than the number ofsubcarriers in the physical resource block.

8. The method of example embodiment any of example embodiments 1-7,wherein the reference signal resource is a CSI-RS resource.

9. The method of any of example embodiments 1-8, wherein each of thecomponents corresponds to two or more subcarriers.

10. The method of example embodiment 9, wherein the two or more ofsubcarriers are adjacent in frequency.

11. The method of example embodiment 9, wherein each componentcorresponds to two or more adjacent symbols.

12. The method of any of example embodiments 1-11, wherein the referencesignal resource is a CSI-RS resource.

13. The method of claim 12, wherein the CSI-RS resource is used toperform CSI measurements with the one or more wireless devices (105).

14. The method of any of example embodiments 1-13, wherein the referencesignal resource is used to perform at least one of:

link adaptation for the one or more wireless devices (105), and

beam management for the one or more wireless devices (105).

15. The method of example embodiment 14, wherein the beam managementincludes beam selection.

16. The method of example embodiment 15, wherein the beam selectionincludes selection of a transmit beam transmitted by a network node(110) and/or a receive beam received by a wireless device (105).

17. A method (400) of obtaining, in a wireless device (105) of awireless communication network (100), an indication of a referencesignal resource in the wireless communication network (100), the methodcomprising:

receiving (S2405) an indication, from a network node (110), of acombination of one or more components contained in one or more physicalresource blocks of a slot; and

using (S2410) the indicated combination of one or more components for areference signal resource.

18. The method of example embodiment 17, wherein the physical resourceblock spans a plurality of subcarriers, and wherein the indication ofthe combination of the one or more components includes an indication ofone or more subcarrier indexes.

19. The method of example embodiment 18, wherein the indication of theone or more subcarrier indexes includes one or more bitmaps.

20. The method of example embodiment 19, wherein each bit in the bitmapuniquely corresponds to a subcarrier index, such that a set bit in thebitmap indicates that a component located at a subcarrier indexcorresponding to the set bit is part of the combination of one or morecomponents used for the reference signal resource.

21. The method of example embodiment 19, wherein a number of bits ineach of the one or more bitmaps depends on a number of subcarriers in acomponent.

22. The method of example embodiment 21, wherein a number of bits ineach of the one or more bitmaps is half a number of subcarriers in thephysical resource block.

23. The method of example embodiment 21, wherein a number of bits ineach of the one or more bitmaps is equal to one less than the number ofsubcarriers in the physical resource block.

24. The method of example embodiment any of example embodiments 17-23,wherein the reference signal resource is a CSI-RS resource.

25. The method of any of example embodiments 17-24, wherein each of thecomponents corresponds to two or more subcarriers.

26. The method of example embodiment 25, wherein the two or more ofsubcarriers are adjacent in frequency.

27. The method of example embodiment 25, wherein each componentcorresponds to two or more adjacent symbols.

28. The method of any of example embodiments 17-25, wherein thereference signal resource is a CSI-RS resource.

29. The method of claim 28, wherein the CSI-RS resource is used toperform CSI measurements with the one or more wireless devices (105).

30. The method of any of example embodiments 17-29, wherein thereference signal resource is used to perform at least one of:

a. link adaptation for the one or more wireless devices (105), and

b. beam management for the one or more wireless devices (105).

31. The method of example embodiment 30, wherein the beam managementincludes beam selection.

32. The method of example embodiment 31, wherein the beam selectionincludes selection of a transmit beam transmitted by a network node(110) and/or a receive beam received by a wireless device (105).

33. A wireless device (105, 200) for facilitating communications in awireless communication network (100) by obtaining an indication of areference signal resource in the wireless communication network (100),the wireless device comprising processing circuitry configured toperform the steps of any of example embodiments 17-32.

34. A network node (110, 300) for configuring a reference signalresource in the wireless communication network (100), the network nodecomprising processing circuitry configured to perform the steps of anyof example embodiments 1-16.

35. A user equipment (UE) (200) for facilitating communications in awireless communication network (100) by obtaining an indication of areference signal resource in the wireless communication network (100),the UE comprising:

an antenna (220) configured to send and receive wireless signals;

a transceiver (215) connected to the antenna and to processing circuitry(205), and configured to condition signals communicated between theantenna and the processing circuitry;

a. the processing circuitry being configured to perform the steps of anyof example embodiments 17-32.

36. A communication system (2800) including a host computer (2810)comprising:

processing circuitry (2818) configured to provide user data; and

a communication interface (2816) configured to forward the user data toa cellular network for transmission to a wireless device (2830),

wherein the cellular network comprises a network node (2820) having:

a communication interface (2826) configured to receive the user data;

a radio interface (2827) configured to interface with a wireless device2830 to forward the user data to the wireless device (2830); and

processing circuitry (2828) configured to perform the steps of any ofexample embodiments 1-16.

37. The communication system of any of the previous example embodimentfurther including the network node.

38. The communication system of any of the previous 2 exampleembodiments, further including the wireless device, wherein the wirelessdevice is configured to communicate with the network node.

39. The communication system of any of the previous 3 exampleembodiments, wherein:

the processing circuitry of the host computer is configured to execute ahost application, thereby providing the user data; and

the wireless device comprises processing circuitry configured to executea client application associated with the host application.

40. A method implemented in a communication system including a hostcomputer, a network node and a wireless device, the method comprising:

at the host computer, providing user data; and

at the host computer, initiating a transmission carrying the user datato the wireless device via a cellular network comprising the networknode, wherein the network node performs the steps of any of exampleembodiments 1-16.

41. The method of the previous example embodiment, further comprising,at the network node, transmitting the user data.

42. The method of any of the previous 2 example embodiments, wherein theuser data is provided at the host computer by executing a hostapplication, the method further comprising, at the wireless device,executing a client application associated with the host application.

43. A communication system (2800) including a host computer (2810) and awireless device (2830), the host computer comprising:

processing circuitry configured to provide user data; and

a communication interface configured to forward user data to a cellularnetwork for transmission to a wireless device (2830),

wherein the wireless device (2830) comprises a transceiver andprocessing circuitry, the wireless device's components being configuredto perform the steps of any of example embodiments 17-32.

44. The communication system of the previous example embodiment, whereinthe cellular network further includes a network node (2820) configuredto communicate with the wireless device.

45. The communication system of any of the previous 2 exampleembodiments, wherein:

the processing circuitry of the host computer is configured to execute ahost application, thereby providing the user data; and

the wireless device's processing circuitry is configured to execute aclient application associated with the host application.

46. A method implemented in a communication system (2800) including ahost computer (2810), a network node (2820), and a wireless device(2830), the method comprising:

at the host computer, providing user data; and

at the host computer, initiating a transmission carrying the user datato the wireless device via a cellular network comprising the networknode, wherein the wireless device performs the steps of any of exampleembodiments 17-32.

47. The method of the previous example embodiment, further comprising atthe wireless device, receiving the user data from the network node.

LIST OF ABBREVIATIONS

TRP—Transmission/Reception Point

UE—User Equipment

NW—Network

BPL—Beam pair link

BLF—Beam pair link failure

BLM—Beam pair link monitoring

BPS—Beam pair link switch

RLM—radio link monitoring

RLF—radio link failure

PDCCH—Physical Downlink Control Channel

RRC—Radio Resource Control

CRS—Cell-specific Reference Signal

CSI-RS—Channel State Information Reference Signal

RSRP—Reference signal received power

RSRQ—Reference signal received quality

gNB—NR base station

PRB—Physical Resource Block

RE—Resource Element

The invention claimed is:
 1. A method of configuring, in a network nodeof a wireless communication network, a reference signal resource in thewireless communication network, the method comprising: obtaining acombination of a plurality of components to be used for a referencesignal resource, the plurality of components being contained in one ormore physical resource blocks of a slot; and indicating, to one or morewireless devices, the combination of the plurality of components in theone or more physical resource blocks that are to be used for thereference signal resource, wherein the physical resource block spans aplurality of subcarriers, and wherein indicating the combination of theplurality of components includes indicating one or more subcarrierindexes, wherein the indication of the one or more subcarrier indexesincludes a bitmap, and wherein each bit in the bitmap uniquelycorresponds to a subcarrier index and a set bit in the bitmap indicatesthat a component located at a subcarrier index corresponding to the setbit is part of the combination of the plurality of components used forthe reference signal resource.
 2. The method of claim 1, whereinobtaining the combination of the plurality of components to be used fora reference signal resource comprises aggregating the plurality ofcomponents across two or more physical resource blocks, to form thereference signal resource.
 3. The method of claim 1, wherein obtainingthe combination of the plurality of components to be used for areference signal resource comprises aggregating one resource element(RE) per port, per physical resource block of the one or more physicalresource blocks of the slot to form the reference signal resource. 4.The method of claim 1, wherein a number of bits in the bitmap depends ona number of subcarriers in a component.
 5. The method of claim 1,wherein the number of bits in the bitmap is half the number ofsubcarriers in the physical resource block.
 6. The method of claim 1,wherein the reference signal resource is a CSI-RS resource.
 7. Themethod of claim 1, wherein each of the components corresponds to two ormore subcarriers, the two or more subcarriers of each component beingadjacent in frequency.
 8. The method of claim 7, wherein each componentcorresponds to two or more adjacent symbols.
 9. The method of claim 1,wherein the reference signal resource is used to perform at least oneof: link adaptation for the one or more wireless devices, and beammanagement for the one or more wireless devices.
 10. A method ofobtaining, in a wireless device of a wireless communication network, anindication of a reference signal resource in the wireless communicationnetwork, the method comprising: receiving an indication, from a networknode, of a combination of a plurality of components contained in one ormore physical resource blocks of a slot; and using the indicatedcombination of the plurality of components for a reference signalresource, wherein the physical resource block spans a plurality ofsubcarriers, and wherein indicating the combination of the plurality ofcomponents includes indicating one or more subcarrier indexes, whereinthe indication of the one or more subcarrier indexes includes a bitmap,and wherein each bit in the bitmap uniquely corresponds to a subcarrierindex and a set bit in the bitmap indicates that a component located ata subcarrier index corresponding to the set bit is part of thecombination of a plurality of components used for the reference signalresource.
 11. The method of claim 10, wherein the indicated combinationconsists of one resource element (RE) per port, per physical resourceblock of the one or more physical resource blocks of the slot.
 12. Themethod of claim 10, wherein a number of bits in each of the one or morebitmaps depends on a number of subcarriers in a component.
 13. Themethod of claim 10, wherein the number of bits in the bitmap is half anumber of subcarriers in the physical resource block.
 14. The method ofclaim 10, wherein each of the components corresponds to two or moresubcarriers, the two or more of subcarriers of each component beingadjacent in frequency.
 15. The method of claim 14, wherein eachcomponent corresponds to two or more adjacent symbols.
 16. The method ofclaim 10, wherein the reference signal resource is a CSI-RS resource.17. The method of claim 16, wherein the reference signal resource isused to perform at least one of: link adaptation for the wirelessdevice, and beam management for the wireless device.
 18. A userequipment (UE) for facilitating communications in a wirelesscommunication network by obtaining an indication of a reference signalresource in the wireless communication network, the UE comprising: anantenna configured to send and receive wireless signals; a transceiverconnected to the antenna and to processing circuitry, and configured tocondition signals communicated between the antenna and the processingcircuitry; the processing circuitry being configured to: receive anindication, from a network node, of a combination of a plurality ofcomponents contained in one or more physical resource blocks of a slot;and use the indicated combination of the plurality of components for areference signal resource, wherein the physical resource block spans aplurality of subcarriers, and wherein indicating the combination of theplurality of components includes indicating one or more subcarrierindexes, wherein the indication of the one or more subcarrier indexesincludes a bitmap, and wherein each bit in the bitmap uniquelycorresponds to a subcarrier index and a set bit in the bitmap indicatesthat a component located at a subcarrier index corresponding to the setbit is part of the combination of a plurality of components used for thereference signal resource.